This invention relates to a saw mechanism for logs convolutely wound on cores and method, and more particularly to a movable disc blade saw which transversely severs elongated logs into retail-size rolls wherein the inventive minimizes log deflection incident to cutting forces.
Exemplary of the type of saw to which the invention pertains is co-owned U.S. Pat. No. 4,821,613. Reference may be made thereto for the background of log sawing and additional details may be seen in co-owned U.S. Pat. No. 4,041,813.
Briefly, for about the last 40 years, paper rolls such as toilet tissue and kitchen toweling webs have been rewound into elongated logs having the diameter of a retail-size roll. These logs were advanced axially past an oscillating or orbiting blade which cut the log into roll segments.
As an illustration, many rewinders were nominally 90" wide so as to provide twenty 41/2" wide toilet tissue rolls. Normally, toweling rolls are 11" wide. In any event, the actual web being rewound into the retail-size roll diameter log was slightly wider than the nominal width--to provide a "trim" portion, thereby avoiding uneven edges. Normally the overall width of the untrimmed web for a 90" rewinder is about 93", permitting a trim of approximately 11/2" at each side of the web, i.e., an annulus having a width of about 11/2" when the trim was removed in the log saw. This trim cutting posed a problem of long standing which has been solved by the instant invention.
The problem is that the last roll cut from the log often shows poor cut quality. This is particularly the case when the roll is softly wound and the core and log compressed due to the cutting forces. The resulting cuts are typically biased, i.e., not perpendicular to the roll center line. The result of this problem is immediately apparent--the last roll may not be of conventional quality and therefore might have to be discarded. Where the log was a "twenty count" log, i.e., 90", this meant jettisioning 5% of the production. Even more importantly, this meant obstruction of the smooth production flow and the obstruction cost often was significant.
The instant invention solved this problem by adding a core support to the log pusher. Here it will be appreciated that for the many years of log sawing, the logs were advanced in troughs so as to pass by the intermittently cutting disc blade. The upstream end of the log was engaged by a pusher, normally carried by an endless chain so as to advance the log past the rotating blade.
By adding the core support to the log pusher, the trim piece (or last roll) can be better supported to minimize the deflections due to the cutting forces. A simple but highly effective mechanism for withdrawing the support out of the core after cutting is provided by fixing a stripper plate to a link in the pusher chain. The link position for the stripper plate is located downstream from the pusher attachment point so that the stripper plate pivots around the chain sprocket before the pusher--thus displacing itself ahead of the pusher. This then strips the trim annulus from the support carried by the pusher--for disposal from the production line.
An additional advantage stems from the employment of the support for the upstream end of the log. This involves the support of the core and therefore the roll itself against undue deflection from the blade entering the periphery of the log. This is particularly helpful where the logs are advanced continuously and the rotating blade also is advanced during the cut. Details of this mechanism can be seen in previously mentioned U.S. Pat. No. 4,041,813. Because the blade is moving axially of the log, there is an initial force applied to the log which is at an angle to the transverse plane of the resulting cut. This is substantially resisted by the pusher support of the invention.
Other objects and advantages of the invention may be seen in the details of construction and operation set forth in the ensuing specification.